Electronic trigger circuit



, diflflfPUT INVENTOR flak/2w N Gwoms BY q ATTORNEY H,- N. CROOKS ELECTRONIC TRIGGER CIRCUIT Flled Sept 28 1951 April 14, 1953 Patented Apr. 14, 1953 ELECTRONIC TRIGGER CIRCUIT Horatio N. Crooks, Haddonfield, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application September 28, 1951, Serial No. 248,839 6 Claims. (01. 315 -168) 1 r This invention relates to bistable state electronic circuits and more particularly to circuits of the type including a gaseous electron discharge tube which may be switched between two stable conditions. Two tube bistable state circuits, such as the Eccles-Jordan trigger circuit found described on page 54 of Time Bases by O. S. Puckle published by John Wiley and Sons, Inc., are well known. These types of circuits have two stable limiting conditions and are driven from on state to the other by externally applied pulses. The two tubes are alternately driven from a conducting to a non-conducting state by pulses of a given polarity being applied, although a two tube bistable state circuit may be used to control or provide an output to a single circuit with successively applied pulses 01' one polarity; Inthis event, one of the two tubes, although required for circuit operation, is not performing any output function. A bistable state circuit which employs only a single tube is more economical for such an application, since both power and circuit component requirements are reduced.

It is an object of the present invention to provide a novel bistable state circuit employing a single tube.

j It is a further object of the present invention to provide an improved and inexpensive single tube bistable state circuit.

Still another object of the present invention is t provide a bistable state circuit employing a single gas tube.

In a copending application of E. 0. Johnson. Serial No.'185,745, filed September 20, 1950, and assigned to the assignee of the present invention, there is described and claimed a gaseous electron tube in which current drawn through the work circuit of the tube may be controlled at all times despite the fact that the tube is ionized. This is performed by providing one source for the tube ionizing current and a second source for the tube work current. By using a separate electrode and a separate source for maintaining the ionizing current, a plasma is generated which surrounds the' anode and cathode of the gaseous tube, and since this plasma (an equal mixture of 1 ions and electrons) is a fairly good conductor, it prevents the formation of a space charge around the cathode. This prevents a space-charge limiting effect and, because the plasma has such a low resistance, a relatively large current may be drawn from the cathode with only. a few volts applied between cathode and anode. Furthermore, as long as the anode voltage does not ex- 2 'ceed the ionizing potential of the gas, the tub can be operated either as a triode, in which case the plate current can be controlled continuously by the grid voltage, or as a diode, in which case the grid is tied to the plate and the plate current can be controlled by controlling the auxiliary discharge current.

Control of the plate current by the grid voltage of this tube is made possible because of the fact that changes in thickness of the positive ion sheaths about the grid wires occur as the grid voltage is varied. The sheaths restrict the plasma cross section and control its electricalv resistance and thus control the plate current. Control of the plate current by controlling the auxiliary discharge current is possible because of the fact that the plate current is proportional to the density of ionization which in turn is proportional to the auxiliary discharge current.

The objects of this invention are achieved by employing a gaseous electron tube, of the type described in detail in the aforesaid application by conducting and non-conducting responsive to these pulses.

The novel features of the invention, as well as the invention itself, both as to its organization and method of operation will best be understood from the following'description when read in connection with the accompanying drawings; in

whichi Figure 1 is a cross section of a gaseous electron discharge tube used in the embodiments of the present invention,

Figure 2 is a circuit diagram of one embodiment of the invention, and

Figure 3 is a circuit diagram of a second embodiment of the invention.

Referring now to Figure l of the drawing, there may be seen a cross section of a gas tube It] used in the embodiments of the invention having a structure essentially such as is described in the above mentioned copending Johnson application. Since details of the tube structure form no part of the present invention, in and of themselves, the tube will be described hereinonly briefly.

The tube has a tube envelope Ill whichencloses the following electrodes. A U-shaped anode l2 encloses a control grid and a main cathode l6. Opposite the open end of the U-shaped anode [2, there is provided an auxiliary cathode [8 which is surrounded by a constricting electrode 20. The constricting electrode has a narrow slit 22 therein extending its full length and positioned opposite the main cathode. 1.6.

The operating characteristicsof .the tube are such that when a voltage greater than the ignition voltage of the tube gas is applied, either between the auxiliary cathode i8 and the main cathode It, or between the auxiliary cathode'and the anode l 2 or both, the tube gas becomes ionized and current flows from the auxiliary cathode to ionize the tube gas. In ionizing the tube gas an ion-electron-plasma is provided which serves as a conductor of current between the main cathode and the anode. This.currentais obtained with a voltage having a much lower .val-ue ..thanthat. required .to ionizethe tube. gas. iThis "flowerf than ionization value.potential may flbesupplied'battery (not shown) connected lbetween the anode and the main cathode. 'A grid ll4 .consisting of grid wires widely spaced ..and..positioned .close to the anode surfaceserves as a control grid and can continuously control the .amount.of..current .whichLis permitted to ."fiow' between the anode .and the main cathode.

LTheslotin the-..constricting electrode. normally ifunctionsjoconcentrate the ionizing currentlso that a .relatively-smalLquantity thereof can prov'iderelatively; high, plasma densities.

.l.Referrin g.no.w;to .Fignre 2, ..a gaseous .electron ll'tube .lll..such as haslbeen fdescribed is.uti1ized, .Ltogether with connections -and ..circuit oom- .gponents lto. providea." bistable .trigger circuit. A source ..of..potentia1...2,3 is ..connectedbetween the main .cathode .and the .:anode ..through .a lload vv.res'is'tor'l l. ilhispotentialisourcellhas a.value less ..than .the .requiriedignitionor ionizing po- .tential..for..thettube.gas. .A pairof. input termi- ...nals 2 6r areprovided to which. negative .pulses may be successively applied. The main .cathode l6 ..and theauxiliary cathode is have .applied to them. apotential which is. between ionization and ..extinction. .potential .for ..the .tube gas. This ,po- .Ltential -source is represented by the battery .28 with. a potentiometer I30, positioned .thereacross for determining-or .settingthis,potential. .The ..main .Icathode I6 ..is .biased ,positively .with ..re- .speot I. to ..the auxiliarycathode .18. vA =difieren- 'tiating circuit '32 couples the inputterminals to the.auxiliary and main cathodes. .Thisdiffer- -entiatingcircuit consists.of=a-resistor..3.4 across 55 -.thelinput terminalsifianda condenser.36 .be- 'tween one..of..the input terminals and the aux- -iliaryeathode it. Themain cathode 1 ii is .con-

nected to the other of the input terminals. .A .resistor 38and a condenser .40. connected in;par- .al-lelare vconnected between the control .grid M and the main cathode [6. In .operation,.negative, pulses when. successively applied to ..the -input terminals"26 servetochangethe tube from a conductingto a non-conducting conditionalternately. Output is derived from the terminals A2 connectedtothe anode it.

"A complete explanation of what occurs isnot "precisely known. .However, it is believed that "whena negativeisignal pulse is applied tothe input terminals 26, thejpulse is differentiated by the differentiating circuit 32 and a negative pulse is-appliedthereby to the auxiliary cathode l8 -asaresult of the frontend of the signal. pulse and a-positive pulse is" applied to the auxiliary cathode at the termination of the signal pulse as a result of the trailing end of the input pulse. The negative pulse tends to send the tube into conduction, the positive pulse tends to send it out of conduction. However, when the tube is sent into conduction a certain amount of time is required for the gas discharge or ionization current to build-up, during which time the volt- 'age betweencathodes drops. -If.the positive go- 10 ing pulse occurs before this voltage between cathodes has dropped too far, the pulse will not extinguish the discharge. If, however, the positive pulse'appears after the auxiliary discharge .currenthas built .up and the voltage between cathodeshas dropped sufliciently, the pulse will extinguish the discharge. Thus, if a negative signal pulse is applied to the tube when in the state of conduction, the negative pulse has no effect on the discharge but the positive pulse turns it ofi.

Whateventhe correct.eXPlanationior therop- .eration of thecircuit maybe, ithas .beendfinitelly established by actual construction of l.the.cir- .cuit'that it operates in response to negative pulses as described. Values'ior one embodiment otthe invention Whichhas been ..constructed.and .op- ,erated. are provide'dlbelow. I

These valuesare not to betaken ..as a. limitation upon the'invention-since thecircuit can function with other circuit component values :as well. The values arelheing.Tfurnished: merely .asan illustrative embodiment oithisinvention.

iResistor 1'2 4,. 5,000. ohms ..Resistor 34, 33,0O0iohms Input'itpulse, volts amplitude Reference is now made tdFigure'twhich shows acircuit diagram of a secondembodiment.otthe present invention. Here alsola potential 23 having a value below that.require'dffor ionizationpf thegas in the tube is applied through a.1oad resistor .2 5 between. the anode i2 and tube main cathode. 16. A second potential M is :provided between themain l6 .andsauxiliaryzcathodes [8 by abattery Aishunted bytagpotentiometerwfi, as was ;previously explained; .to obtain. a potentialhaving a value between that1'eq.u-ir.ed. for ignition and extinctionofthe tube gas. :Apair of 1pulse. input. terminalslfi: are provided with"a differentiating circuit A8 connecting the input 'terminalsto the. main l6 and auxiliary cathodes Hi. ,This differentiatingv circuit ifilconsists ofxa .first resistor Eil connected across theterminals .26 .anda condenser :52 connected fromone jof 'jsai'd'terminals to theauxiliary cathode. -A con denser 54 also connects .the same. one of the in- "putterminals'to thecontrol grid l4. :A second resistorlfifiis connected between the control grid Hand themain cathodelS of .thetube. The constricting electrode .20 .is also connected to the auxiliary cathode.

When positive pulses are successivelyapplied to'th'e inputterminals 26, the .tube illswitches from conduction to non-conduction alternately in response to the successive pulses. Aspecific explanation for .the operation ofthis= circuit is also not completely known. However, it :is thought that the positive input pulses which are applied tothe-inputterminals appear on both aca emic.

Although the initial pulse height is the same" onboth electrodes, the time constant of'the auxiliary cathode circuit is 'inuch' smaller than that of the grid circuit so that the duration of the pulse'on'the grid'is longerrthan that of the pulse on the auxiliary cathode and, the turn-on effect of theagridapulse overcomes the turn-olfeii'ect of the auxiliary. cathode pulse. Thus, when the tube is in a non-conducting state anda positive pulse is applied to the circuit, the tube is sent into a state of conduction.

When the tube is in the conducting state, the

collection of electrons by the grid causes it to as-j sume a negative potential. The actual measure ments showed the grid to be negative when the tube is conducting by about 20 volts as compared to 3 volts in the non-conducting state. As a re' suit, the pulses appearing on the grid have less turn-on effect when the tube is conducting than when it is non-conducting. Consequently, the circuit can be adjusted so that when the tube is in the conducting state, the turn-01f effect of the auxiliary cathode pulses is larger than the turnon eifect of the grid pulses, and the tube is sent into the non-conducting state. Thus, the tube can be sent into alternate states of conduction and non-conduction by a succession of positive pulses.

Regardless of the explanations for the opera-v tion of the embodiment of the circuit shown in Figure 3 of the drawing, the circuit has been actually constructed and operates exactly as described. As an example of the circuit component values required for one embodiment of the invention and not to be construed as a limitation of the invention, the following component values are provided:

Resistor 24, 5,000 ohms Resistor 50, 33,000 ohms Resistor 56, 220,000 ohms Potentiometer 46, 2,500 ohms Condenser 48, 0.25 mmf. Condenser 54, 0.25 mmf. Battery 44, 90 volts Battery 23, 16 volts Input pulse amplitude, 45 volts From the above description, it will be seen that a novel, useful, bistable trigger circuit, which is responsive to pulses of single polarity to successively go from one stable state to a second stable state, has been described.

What is claimed is:

1. A bistable state circuit comprising a gaseous electron tube including an anode, a control grid, a main cathode, an auxiliary cathode and a constricting electrode enclosing said auxiliary cathode and having an opening opposite said main cathode, means to apply between said main cathode and anode a first potential having a value less than the ionization potential of said tube gas,

means to apply between said auxiliary cathode and said main cathode a second potential having a. valu between the ionizing and extinction potential of said tube gas, and means to apply successively pulses of one polarity to said main cathode, said control grid and said auxiliary cathode 6 to" renden said tube alternatelycondiieting and non-conducting responsiveto saidsuccessive ones of said pulses.

2. A bistable trigger circuitcomprising a game-- ous= electron tube having a plurality of electrodes including an anode, a control grid, a main oathode, arr auxiliarycathode and aconstricting electrode enclosing said auxiliary cathode-and hav=- ing an opening opposite-said main cathode, means to apply between said main cathod'eand anode a' first potential having avalue less than the ionization potential of said tube gas; means to apply between said auxiliary cathode and saidmain cathode a second potential having a value between the ionizing and extinction potentialpf' said'tube'gas, and means includinga difierentiatmg circuit connected between saidmain cathode and one of said other electrodesto apply-pulses of'one' polarity between said main" cathode and said one of said other electrodes to render said tube alternately conducting and non-conducting responsive to successive ones of said pulses.

3. A bistable state trigger circuit comprising a gaseous electron tube including an anode, a control grid, a main cathode, an auxiliary cathode and a constricting electrode enclosing said auxiliary cathode, and havin an opening opposite said main cathode, means to apply a potential having a value less than the ionization potential of the gas in said tube between said main cathode and anode, means to apply between said main and auxiliary cathodes a potential having a value between the ionization and extinction potential of the gas in said tube, a pair of pulse input terminals, a diiferentiating circuit coupling said input terminals to said main and auxiliary cathodes, and means coupling said control grid to one of said pair of input terminals, whereby a successive application of negative pulses to said pulse input terminals renders said tube alternately conducting and non-conducting.

4. A bistable state trigger circuit comprising a gaseous electron tube including an anode, a control grid, a main cathodean auxiliary cathode and a constricting electrode enclosing said auxiliary cathode, and having an opening opposite said main cathode, means to apply a potential having a value less than the ionization potential of the gas in said tube between said main cathode and anode, means to apply between said main and auxiliary cathodes a potential having value between the ionization and extinction potential of the gas in said tube, a pair of pulse input terminals, said main cathode being connected to one of said terminals, a condenser connected between said auxiliary cathode and the other of said terminals, a resistor connected between said pair of terminals, and means coupling said control grid to one of said pair of terminals.

5. A bistable trigger circuit comprising gaseous electron discharge tube including an anode, a control grid, a main cathode, an auxiliary cathode and a constricting electrode enclosing said cathode and having an opening opposite said main cathode, means to apply a potential having a value less than the ionization potential of the gas in said tube between said anode and main cathode, means to apply between said main and auxiliary cathodes a potential having a value between the ionization and extinction potentials of the gas in said tube, a pair of pulse input terminals, said main cathode being connected to one of said pair of terminals, a first condenser connected between said auxiliary cathode and the other of said terminals, a first resistor connected across said pair ofterminals, a second condenser connected between. said control rid and said other of said pair of terminals, and a second resistor connected between said control grid and said main cathode, whereby a successive application of positive pulses to said pulse input terminals renders said tube alternately conducting and non-conducting.

6. A bistable trigger circuit comprising a gaseous electron discharge tube including an anode, a control grid, a main cathode, an auxiliary cathode and a constricting electrode enclosing said cathode and having an opening opposite said main cathode, means to apply a potential havine a value less than the ionization potential of the gas in said tube between said anode and main cathode, means to apply between said main and auxiliary cathodes a potential having a value between the ionization and extinction potentials HORATIO N. CROOKS.

References Cited in the file of this patent UNITED STATES PATENTS Name Date Number Johnson Apr. 8, 1952 

